A man was taken to hospital following a serious accident on the A9 at Birnam on Friday November 15.
Officers are continuing their enquiries and are now appealing for information from the public.
The crash took place around 6.22pm and involved a Range Rover Sport, an MG 4 and a Fiat 500 L.
Police and ambulance attended and a 53-year-old man, the driver of the MG, was taken to Ninewells Hospital in Dundee.
The five men within the Range Rover and a woman who was driving the Fiat were uninjured.
A woman who was a passenger in the MG was treated by ambulance staff.
Sergeant Steve Livesey said: “Our enquiries are continuing into the cause of this crash. I would urge any witnesses or anyone with information to contact us.
“We are very keen to identify and trace an abnormal load which was being driven southbound on the A9 between Bankfoot and Birnam at the time of the crash.
“Any drivers with dashcam who were on this road around the time of the crash are asked to review their footage and please contact us if it holds anything relevant.
“Anyone with information should contact 101 quoting incident number 3111 of November 15.”